I JUST FOUND IT
The article compared large weekly water changes to more frequent smaller water changes.
But now I have another question
Does doing larger water changes impact the fish's osmoregulatory system? My reason for asking:
I used to do 30% water changes but now I do 40-50% because I am now fully stocked. I was thinking that taking out half the water makes a pretty sudden change in the tank--the bottom layer (ie the one with the most weight on it) is now gone and there's only "lighter" pressure in the tank (for my pleco or loaches, for example, that would be robbing them of their pressure zone pretty suddenly). (Kind of like us going on an airplane and the ear pressure deal).
I started doing a back to back 20-30% WC to 1) lessen the pressure differential during the WC and 2)keep my filter going because right around 30% it can't suck up water and makes a weird noise that's hard on the motor. Does this matter? Does the osmoregulatory function work faster than the rate of the pressure loss during the WC?